INVESTIGATION OF TRAPS IN beta-Ga2O3:0.05%Cr AND beta-Ga1,9In0,1O3:0,05%Cr CRYSTALS BY FRACTIONAL THERMAL-GLOW TECHNIQUE

Abstract

The research results of the luminescence spectra and thermally stimulated luminescence (TSL) in β-Ga 2 O 3 and β-Ga 1,9 In 0,1 O 3 single crystals doped with chromium ions, grown by the optical melting zone method, have been presented. The Cr 3+ impurity concentration was 0.05%. Luminescence was excited by light with a wavelength of 440 nm from the region of the broad absorption band 4 A 2 → 4 T 1 of Cr 3+ ions. Two sharp R-lines ( 2 E → 4 A 2 transitions) are dominated in the luminescence spectrum of investigated samples at the temperature of liquid nitrogen. A number of weak narrow lines associated with the phonon-induced sidebands of the R -lines are observed in the wavelength range of 700-740 nm. At room temperature, a broad luminescence band extending from 650 to 900 nm is dominated and corresponds to electron-vibrational 4 T 2 → 4 A 2 transitions in chromium ions. The R -lines are also observed on the background of this broad luminescence band in the luminescence spectrum of chromium impurity in gallium oxide at room temperature. The luminescence of chromium impurity in solid solutions is concentrated only in a broad luminescence band with a maximum near 775 nm ( 4 T 2 → 4 A 2 transitions). Doping of β-Ga 2 O 3 with a chromium impurity leads to the appearance of a thermoluminescence maximum at 285 K, which corresponds to traps with an energy depth of 0.59 eV. In the crystals of the solid solution, there is a shift of the TSL maximum to the range of low temperatures up to 225 K and an increase in its half-width. The fractional thermal-glow technique was used to analyze the TSL complex maximum at 225 K. It was established that this maximum consists of at least 4 elementary maxima, which are caused by the release of electrons from traps with activation energies in the ranges of 0.4-0.42 and 0.48-0.495 eV. The method of the initial increase in the intensity of the TSL glow was used to calculate the activation energy. Keywords : β-Ga 2 O 3 , solid solutions, thermally stimulated luminescence, activation energy.